An authority has spent £1.7m assessing the works of collapsed firm Carillion, a new report has revealed.
It also shows Oxfordshire County Council spent £123m on a total of 602 projects with the company, which went into liquidation in January.
Building projects carried out by Carillion had missing certificates and fire safety issues, the report said.
The council said it would be claiming back the costs from Carillion's liquidators.
The construction giant provided school meals and cleaning, maintenance of council buildings, property services and building work.
The council signed a 10-year contract with the firm in 2012, but last year agreed to transfer back most services except facilities management.
'Range of issues'
In total 17 schools were affected by the firm's collapse.
One example saw Sutton Courtenay Primary School left with its playground half-finished, and children in temporary classrooms for months.
The report shows the authority has looked at 162 of the biggest projects carried out by Carillion.
It identified a "range of issues", including missing contract and building control certification, missing Health & Safety and maintenance manuals, and "unsatisfactory fire strategies and planning conditions not fulfilled, to major elements unsuitably executed".
"Given the scale and extent of the issues", the report said, it would be "expedient" to review the costs to confirm how much was required to "fund the defects programme".
Alexandra Bailey, director for capital investment and delivery at the council, said the figure owed by Carillion was "likely to be significant but it's really, really important that we go through the due diligence".
"We've had the surveys completed and we're now assessing the likely cost," she said.
The council is expecting to release the figures after Christmas as part of its budget-setting process.